At least some known wind turbine generators include a rotor having multiple blades. The rotor is sometimes coupled to a housing, or nacelle, that is positioned on top of a base, for example, a truss or tubular tower. At least some known utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) have rotor blades having predetermined shapes and dimensions. The rotor blades transform mechanical wind energy into induced blade lift forces that further induce a mechanical rotational torque that drives one or more generators via a drive train that includes a rotor shaft, subsequently generating electric power. The generators are sometimes, but not always, rotationally coupled to the rotor shaft through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor shaft for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into the electric utility grid. Gearless direct drive wind turbine generators also exist.
During operation of such known wind turbine generators, the rotor may experience a mass imbalance, thereby inducing increased loads on the rotor and other drive train components. Also, the rotor's position with respect to the wind may induce increased loads on the rotor and other drive train components. The associated gear boxes and drive train components may also experience failures. Failures of such known wind turbines may also include drive systems, control gears, transmissions, bearings, drive shaft imbalances, and mounting bushings. Environmental stresses and mechanical failures over the operation of the turbine generators results in changes and shifts to the vibrational frequencies and angular velocity fundamental signals which are indicative of a developing fault.
One commonly employed technique is to examine the individual frequencies present in the signal. These frequencies correspond to certain mechanical components (for example, the various pieces that make up a known wind turbine generators rolling-element bearing) or certain malfunctions (such as shaft imbalance or misalignment). By examining these frequencies and their harmonics, analysis can often identify the location and type of problem, and sometimes the root cause as well. For example, high vibration at the frequency corresponding to the speed of rotation is most often due to residual imbalance and is corrected by balancing the drive shaft. As another example, a degrading rolling-element bearing will usually exhibit increasing vibration signals at specific frequencies as it wears. A condition monitoring system can provide an analysis that is able to detect this wear weeks or even months before failure, giving ample warning to schedule replacement before a failure which could cause a much longer down-time.
Another commonly employed technique is to measure the voltage and current output of a constant-speed wind turbine generator to ensure power output. Additionally, variable-speed wind turbines can (very briefly) produce more power than the current wind conditions can support which causes additional strain on the power transformers of the wind turbine generator.
The present invention is directed to overcoming these and other deficiencies in the art.